Smelting iron ore



June 8, 1943. T, V. MOORE smmme IRON ORE Filed Feb. 14, 1941 7750mm KmINVENTOR.

AT TORN E Y Patented June 8, 1943 SMELTING IRON ORE Thomas V. Moore,Houston, Tex., assignor to Standard Oil Development Company, acorporation of Delaware Application February 14, 1941, SerialNo. 378,870

2 Claims.

The present invention is directed to a method for recovering iron fromiron ore and particularly to a method which permits the utilization ofgas, both as fuel and as a reducing agent. In a copending application,Serial No. 313,371, filed January 11, 1940, which matured into PatentNo. 2,292,579, dated August 11, 1942, and entitled Reduction of ironores, there has been described a method for utilizing gas in therecovery of iron from iron ore according to which the reduction step inthe recovery process is carried out at a temperature above the meltingpoint of pure iron, in order to avoid the plastic stage through whichiron passes in going from a solid to a liquid. The method described insaid co-pending application involves the use of a rotary kiln.

According to the present invention, gases are used for the recoveryofiron from iron ore in a continuous method carried out preferably in avertical stationary tower. The method involves a plurality oi stageswhich, in order, are the preheating stage, the reduction stage, and thecarburizing stage. The reduction stage is carried out at a temperaturebelow the melting point of pure iron but above the melting point ofiron-carbon alloy, which is formed in the carburizing stage.

Briefly, the method of the present invention 'comprises passing powderediron oxide, with 'mixture passes countercurrent to a stream of hydrogencarrying sufiicient air to burn enough of the hydrogen to maintain thetemperature desired but, of course, insufiicient air to render the gasan oxidizing gas as distinguished from a reducing gas. Next, the mixturepasses countercurrent to a carburizing gas, that is, a hydrocarbon gaswhich, at the temperature of operation will decompose to supply hydrogenand thermatomic carbon so that the latter may combine with the reducediron to form a low melting alloy of iron and carbon.

The nature of the present invention'will be more clearly understood fromthe following detailed description of the accompanying drawing, thesingle figure of which is a schematic view in section of an apparatussuitable for the practice of the present invention. Referring to thedrawingin detail, numeral l designates a tower, the upper portion 2 ofwhich is of somewhat enlarged diameter. Arranged around the bottom ofportion 2 is a manifold 3 to which gas is fed by tubes 6. At the upperend of portion 2 of the tower is an outlet 5 for gas and an inlet 6 forpowdered iron oxide and slag-forming materials. At this point'it shouldbe noted that the apparatus will be provided with suitable equipment,such as none hoppers or the like, for the introduction of the iron oreand the slag-forming constituents and the distribution thereof acrossthe section of the tower but these details are omitted here since theyform no part of the present invention. It will also be understood thatthe manifold 3 will be of one of the approved constructions for suchdevices commonly used in the blast furnace art but is shown here onlydiagrammatically for the sake of clarity.

At a suitably selected point below portion 2 of the tower is arranged aninlet i for hydrogen and air; Here it should be noted that the hydrogenis introduced through a ring manifold or tuyre or through some otherequivalent appliance an internal ring-shaped nozzle such commonly knownin the art for distributing the gas throughout the falling mass ofmaterial. The

hydrogen itself .is preferably prepared from natpreferably in theneighborhood of 1300 C.

At a point suitably spaced from the point of introduction of thereducing gas, and below it, is arranged another inlet 8 for carburizinggas.

\ Here, again, the gas will be introduced through a suitable device fordistributing it throughout the mass. At this point ahydrocarbon gas maybe employed, natural gas being preferred. This gas is also preheated toa temperature somewhat above that maintained in the reduction zone andis accompanied by a quantity of air sufficient to maintain the desiredtemperature, which will be substantially the same as the temperaturemaintained in the reduction zone and in any case above about 1,000 C.When methane or other hydrocarbon gas is used at this point, it iscracked to hydrogen and thermatomic carbon. The former passes upwardlyand assists in, the

reduction stage. The latter is deposited in the falling mass andcombines with the iron in this mass to produce the low-meltingiron-carbon alloy, commonly known as plgiron, which settles to thebottom and may be drawn oil through an outlet 9. The second outlet I isarranged at a higher point for withdrawing slag.

Instead of introducing a hydrocarbon gas at point 8 there may beintroduced a suspension of finely divided carbon such as thermatomiccarbon, which may be obtained from the pyrolysis of hydrocarbon gas usedfor the production of the hydrogen introduced at point I. This carbonmay be suspended in a non-oxidizing gas containing sumcient air toprovide, by combustion with a portion of the carbon, suilicient heat tomaintain the desired temperature.

As has been previously indicated the iron ore is used in powdered form.It is introduced at such a rate with respect to the velocity of thevarious gas streams that it is partly supported by the upfiowing gaswhereby it moves downwardly through the vessel slowly. When the iron oreis suifici ently pure the addition of slag-forming constituents may beomitted. Where the iron ore contains considerable high meltingimpurities which must be removed, however, it is desirable to add slagforming material to the charge. In order to avoid any possibility of theslag interfering with the reduction and carburizing stages it ispreferred, according to the present invention, to add the slag formingmaterial in the form of lumps which are quite large relative to the ironore so that these lumps will have notendency to produce a coating ofslag on the particles of iron ore and will descend through the vessel ata much more rapid rate than the iron ore. Since it is only near thebottom of the vessel that the slag-forming constituents actually performtheir function, it is unnecessary to provide for any intimate mixture ofthese constituents with the iron ore in the higher levels of the vessel.In practice this slag can be added in lumps ranging in size from aboutpea size to relatively large lumps, as large as egg size.

In operating according to the present invention it is important toselect a vessel of suitable diameter to enable the partial suspension ofthe iron ore by the gas without using an excessively high velocity andtherefore aprohibitively large quantity of the gas. The vessel to beused should be designed with various factors in mind such as theparticle size of the iron ore to be used, the heat input intotheseparticles from the gas, the

amount of gas which can economically be used, the velocity of the gasrequired to regulate the falling rate of the particles, etc. The vesselwill, of course, be supplied with suitable insulation and with heatexchangers at appropriate points for economical operation.

The nature and objects of the present invention having been thusdescribed and illustrated, what is claimed as new and useful and isdesired to be secured by Letters Patent is:

1. A method for recovering iron from iron ore which comprises droppingiron ore, in a finely divided state, together with slag forming materialin discrete form heavier than the ore particles through a rising streamof gas which is of a diflerent composition at difierent levels, being ofan oxidizing nature at the uppermost level and a reducing nature at alower level, and adjusting the velocity of the gas so as to cause theore to drop at a retarded rate so regulated as to maintain the particlesin each zone for the desired period.

2. A 'method for recovering iron from iron ore which comprises droppingiron ore, in a finely divided state, together with slag forming materialin discrete form heavier than the ore particles through a rising streamof gas which is of a diiierent composition at difierent levels, being ofan oxidizing nature at the uppermost level, a reducing nature at thenext lower level, and a carburizing nature at the next lower level, andadjusting the velocity of the gas so as to cause the iron ore to-drop ata retarded rate so regulated as to maintain the particles in each zonefor the desired period.

THOMAS V. MOORE.

